Chiang et al U.S. Pat. No. 4,133,698 is directed to a tandem junction solar cell having a P-type monocrystalline silicon substrate. The illuminated front surface is textured while an interdigitated P-N junction is located on the nonilluminated back surface. An unconnected front junction forms a "floating" junction which suppresses front surface recombination and enhances collection at the back side junction. A metallized back surface contact has a geometry which matches that of the P-N junction.
Nicoll U.S. Pat. No. 2,999,240 is concerned with photovoltaic cells of sintered materials. The cells have interdigitated electrodes of copper and silver pastes.
Evans et al U.S. Pat. No. 4,104,091 describes the use of screen printing to apply diffusants onto both surfaces of a semiconductor solar cell. One type of dopant is applied to the front surface of the substrate by this technique. An opposite type of dopant is applied to the back surface.